Heat sinks are so-called extended surfaces that have been used to enhance cooling of heat dissipating surfaces. Such heat sinks have been fabricated in a number of designs. The designs are such as to decrease fluid flow impedance through the heat sink and, thereby, improve heat dissipation performance. The pin fin heat sink is of particular interest because it is one of the commonly used heat sinks.
FIGS. 1 and 2 show prior art pin fin heat sinks. FIG. 1 is a top view of pin fin heat sink 100 showing fluid flow (gas or liquid) relative to the heat sink. Heat sink 100 includes a base surface 101 having a plurality of pin fins 102 perpendicular to and protruding therefrom. In this example, pin fins 102 are in staggered rows. Pin fins 102 could equally be in aligned rows on base surface 101. It is noted and has been observed by me that after approximately the first two (2) rows of the pin fins, the fluid flow loses a significant amount of its inertial force and tends to slow, potentially becoming quasi-stagnant (herein after referred to as stagnant). Thus, as seen in FIG. 1, the normal fluid flow at velocity V1 is supplied in the left-to-right direction. The fluid flow begins to slow down after a few rows of pin fins and has a velocity of V3. In this example, the fluid around the heat sink increases to velocity V2 and part of it is entrained into the right side of the heat sink against the normal direction of flow. It has also been observed that velocity V2 is approximately twice V1 (V2.perspectiveto.2V1) and the velocity V2 is very much greater than V3 (V2&gt;&gt;V3). FIG. 2 shows a side view of the pin fin heat sink 100. FIG. 2 illustrates that because of the fluid back flow being entrained into the right side of the heat sink that the fluid entering from the left is forced to flow out of the top of the pin fins 102. The stagnation of the fluid flows also contributes to the fluid exiting from the top rather than flowing completely through the pin fins of the heat sink. Consequently, the fluid flow process described contributes to inefficiencies in dissipating heat from the surface to which the heat sink is attached.